The present invention relates generally to cardiac rhythm management systems. In particular, the present invention relates to detection of lead displacement or migration of a sensing/pacing lead, such as a left ventricular lead within the coronary sinus, coronary veins or one or more epicardial or pericardial locations.
In 1957, the first wearable, battery-powered cardiac pacemaker was used to keep a young patient alive. The first implantation of a permanent pacemaker followed in 1958. Since then, pacemaker technology has continually improved and has become the treatment of choice to treat symptoms due to bradycardia. The pacing lead is usually introduced transvenously into the right atrium or right ventricle, and electrical pulses from the implanted pacemaker are applied by the lead via metal electrodes that are in contact with cardiac muscle.
More recently, cardiac resynchronization therapy using bi-ventricular pacing has been introduced to treat patients with heart failure. More than twenty million people worldwide suffer from heart failure, with about two million new cases diagnosed each year. With some patients, heart failure disease affects the synchronous beating action of the left ventricle and right ventricle until the left ventricle cannot pump blood efficiently to supply the body with oxygen and nutrients. These patients tend to tire easily, have a poor quality of life, and their health may deteriorate rapidly resulting in a need of a heart transplant or death.
Cardiac resynchronization therapy helps to coordinate the left ventricle and right ventricle of the heart in patients with moderate to severe heart failure. It helps to improve the pumping power of the heart, can make the patients feel better, increase their energy levels, and improve their exercise capacity.
Cardiac resynchronization therapy systems typically include a left ventricular lead to provide stimulation to the left ventricle, together with conventional pacing leads placed in the right atrium and right ventricle.
The left ventricular lead is oftentimes introduced via the coronary sinus into the coronary venous system to achieve appropriate (synchronous) left ventricular stimulation although a variety of epicardial or pericardial locations can also be utilized. Different patients have different cardiac venous anatomy. As a result, delivery of a left ventricular lead can be challenging. In addition, heart failure can result in cardiac remodeling or change of shape. In contrast to the electrodes of the right atrial pacing lead and the right ventricular pacing lead, which are typically affixed to cardiac muscle by a fixation mechanism such as tines or a screw tip, the electrode (or electrodes) of the left ventricular lead are positioned within a blood vessel and are not affixed by a fixation mechanism. Given the location and the lack of tissue fixation, maintaining the position of the left ventricular lead on a long-term basis can be difficult to achieve. The inventors suggest that in approximately twenty percent (20%) of patients, the left ventricular lead suffers some dislocation, and stimulation may become less effective because the electrode is no longer positioned in the clinically optimal position.